Re: Where can I find seeds?

As far as I can tell, you're asking about what are called consumables, or spawnable pots.  You start the game with a few, but you have to get more by buying sticker packs.  Go to the sticker shop and get some of 2,500 coin minion packs.  You'll get an assortment of items for both plants and zombies - some for those pots (or graves for zombies) and some that you spawn from dirt plies in multiplayer.